I cannot seem to figure why my 77 hesitates- and sounds like crap, when I blip the throttle to shift down or ready to take off. Once under way it has real good power and is smooth all the way up and all the down the rpm range. I have the old black box ignition and have done the bypass trick for that I've done the off idle jet fix. I've been through the carbs a few times. They are very clean. Could this just be one, or more, slides that don't pull up evenly? Under load, they must pull up a bit slower, where as at idle or no load, maybe one is hanging behind the others. I've polished the slides, but I think that is where I'll look again. Any other suggestions?